A conventional microwave oven is disclosed in Patent Literature 1. This microwave oven is provided with a heating chamber in which a cooking object is placed, and the microwave oven incorporates a magnetron which oscillates in response to application of voltage, to thereby generate a microwave. The microwave generated by the magnetron is supplied into a heating chamber, where a cooking operation is performed with respect to the cooking object.
In addition, the microwave oven is provided with a timer which counts driving time of the magnetron. The driving time of the magnetron counted by the timer is stored in an accumulated manner as cumulative driving time. When the cumulative driving time of the magnetron exceeds a predetermined length of replacement time, it is judged that the life of the magnetron is close to its end, and a notice is given to the effect that it is time to replace the magnetron through a display portion or the like.
This notice enables a user to replace the magnetron before its life expires and the magnetron stops working. Thus, it is possible to prevent failure of cooking caused by the magnetron stopping in the middle of a cooking operation. Furthermore, in the case of a business-use microwave oven, the magnetron can be replaced out of business hours, and this helps avoid downtime of the microwave oven, to thereby prevent reduction of the operating ratio of the microwave oven.